Polyimide film and method for producing the same

Abstract

The present application relates to a kind of polyimide film and its preparation method, the preparation method is dissolved in DMAC by NBDA and / or M-Tol, N2 is passed, stirring is completely dissolved, and mixed solution is obtained;BPADA or ODPA is added to mixed solution, the passage of N2 is maintained, after a period of time, PAA glue liquid is obtained;PAA glue liquid is dropped on tool plate, is coated uniformly on the tool plate according to the thickness required, is placed into oven, and heat imidization is carried out, then tool plate is taken out, and naturally cooled to room temperature, then tool plate is placed into warm water, until the film coated on tool plate is detached from the tool plate, then the film is placed in oven and dried, and after cooling, polyimide film is obtained.The preparation method of the polyimide film of the present application is simple, environmentally friendly, and the polyimide film of the present application has good optical transparency and thermal performance.

Description

TECHNICAL FIELD

[0001] The present application relates to high molecular materials, in particular to a layered product consisting essentially of synthetic resin, and more particularly to a protective film such as a polyimide film, and to a method of manufacturing the protective film, i.e. the polyimide film. BACKGROUND

[0002] Polyimide (PI) is a kind of high-performance polymer containing repeating imide ring units in the main chain. Its special structure makes it have excellent chemical resistance, radiation resistance, thermal stability and other properties, and it is widely used in aerospace engineering, microelectronics, automotive field and other fields. PI has been processed into various types of materials, such as films, coatings, foams, fibers, adhesives, etc. Among all kinds of PI products, film is one of the most dominant types, which is widely used in packaging, microelectronic manufacturing, solar substrate field, etc. such as flexible printed circuit (FPC) base film, chip scale packaging (CSP), etc. However, the traditional aromatic PI presents deep brown or deep yellow brown due to the charge transfer complexation (CTC) between the molecular chains, which limits its application in the field requiring high optical transparency and display devices. Therefore, the development of various excellent performance light-colored transparent PI film has become a hot research topic and a difficult point to overcome for researchers. SUMMARY

[0003] The technical problem to be solved by the present application is to avoid the shortcomings of the prior art and provide a polyimide film and a preparation method thereof. The preparation method of the polyimide film of the present application introduces a cheap peraliphatic diamine into the polyimide (PI) chain. The peraliphatic diamine is a homochiral monomer with a norbornane skeleton structure, which can effectively reduce the charge transfer complexation between the molecular chains. On this basis, aromatic diamine is introduced to prepare a light-colored polyimide (PI) film with high transparency and good thermal properties. The polyimide film of the present application has high thermal stability and light-colored transparency.

[0004] The technical solution adopted by the present application to solve the technical problem is as follows:

[0005] A preparation method of a polyimide film is provided, which comprises the following steps in sequence:

[0006] Step A: Dissolve the diamine monomer bicyclo[2.2.1]heptane dimethylamine or 2,2'-dimethyl-4,4'-diaminobiphenyl in a solvent N,N-dimethylacetamide, introduce nitrogen, and stir until completely dissolved to obtain a mixed solution;

[0007] Step B: To the above mixed solution, bisphenol A diether dianhydride or 4,4'-oxybisphthalic anhydride is added, and nitrogen is kept flowing, and after a period of reaction, a polyamic acid glue solution is obtained;

[0008] Step C: The above polyamic acid glue solution is dropped on a tool plate, and is coated uniformly on the tool plate to a desired thickness, and is placed in an oven for thermal imidization, and then the tool plate is taken out and naturally cooled to room temperature, and then the tool plate is placed in warm water until the film coated on the tool plate falls off from the tool plate, and then the film is placed in an oven for drying, and after cooling, a polyimide film is obtained.

[0009] The molar ratio of the bisphenol A diether dianhydride or 4,4'-oxybisphthalic anhydride to the bicyclo[2.2.1]heptanediimine or 2,2'-dimethyl-4,4'-diaminobiphenyl is (1-1.02):1.

[0010] Alternatively, another method for preparing a polyimide film is provided, which sequentially comprises the following steps:

[0011] Step A: Bicyclo[2.2.1]heptanediimine and 2,2'-dimethyl-4,4'-diaminobiphenyl of a diamine monomer are dissolved in a solvent N,N-dimethylacetamide, nitrogen is flowed, and stirring is performed until complete dissolution, so as to obtain a mixed solution;

[0012] Step B: To the above mixed solution, bisphenol A diether dianhydride or 4,4'-oxybisphthalic anhydride is added, and nitrogen is kept flowing, and after a period of reaction, a polyamic acid glue solution is obtained;

[0013] Step C: The above polyamic acid glue solution is dropped on a tool plate, and is coated uniformly on the tool plate to a desired thickness, and is placed in an oven for thermal imidization, and then the tool plate is taken out and naturally cooled to room temperature, and then the tool plate is placed in warm water until the film coated on the tool plate falls off from the tool plate, and then the film is placed in an oven for drying, and after cooling, a polyimide film is obtained.

[0014] The molar ratio of the bisphenol A diether dianhydride or 4,4'-oxybisphthalic anhydride to the total amount of the bicyclo[2.2.1]heptanediimine and 2,2'-dimethyl-4,4'-diaminobiphenyl is (1-1.02):1; and the molar ratio of the bicyclo[2.2.1]heptanediimine to 2,2'-dimethyl-4,4'-diaminobiphenyl is (10-0):(0-10).

[0015] In step A, the mass percentage of N,N-dimethylacetamide in the mixed solution is 15%-25%.

[0016] In step C, the oven is heated imidized according to 80 ℃ / h (vacuum), 120 ℃ / h (vacuum), 150 ℃ / h (vacuum), 200 ℃ / h, 250 ℃ / h.

[0017] The present application also provides a polyimide film, which is obtained by the above-mentioned method for preparing a polyimide film, and specifically, the polyimide film comprises N,N-dimethylacetamide, and a bisphenol A type diether dianhydride or 4,4´-oxydiphthalic anhydride, and a diamine monomer of bicyclo[2.2.1]heptane dimethylamine and / or 2,2'-dimethyl-4,4'-diaminobiphenyl.

[0018] Compared with the prior art, the polyimide film and the method for preparing the same have the following advantages:

[0019] The method for preparing the polyimide film of the present application uses N,N-dimethylacetamide (DMAC) as a solvent, and a diamine monomer of bicyclo[2.2.1]heptane dimethylamine (NBDA) and / or 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol), and a bisphenol A type diether dianhydride (BPADA) or 4,4´-oxydiphthalic anhydride (ODPA) to synthesize a high-thermal-stability light-colored or even colorless transparent polyimide film; the high-thermal-stability light-colored or even colorless transparent polyimide film obtained by the method for preparing the polyimide film of the present application adopts a binary polymerization and ternary copolymerization mode, the binary polymerization mode is used to obtain a high-thermal-stability light-colored or even colorless transparent polyimide film, and on the basis of the binary polymerization mode, the ternary copolymerization mode is used to introduce an aromatic diamine M-Tol to obtain a light-colored or even colorless transparent polyimide film with good optical transparency and thermal performance; the method for preparing the polyimide film of the present application is simple and environmentally friendly; and the polyimide film of the present application has good optical transparency and thermal performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The figure is a Fourier infrared spectrum of each embodiment of the polyimide film of the present application;

[0021] Figure 2 The figure is an ultraviolet transmittance spectrum of each embodiment of the polyimide film of the present application;

[0022] Figure 3 The figure is an ultraviolet data list of each embodiment of the polyimide film of the present application;

[0023] Figure 4 The figure is a differential scanning calorimetry (DSC) curve of each embodiment of the polyimide film of the present application;

[0024] Figure 5 The figure is a thermogravimetric analysis (TGA) curve of each embodiment of the polyimide film of the present application;

[0025] Figure 6 is the differential thermal gravimetric analysis (DTG) curve of each embodiment of the polyimide film of the present application;

[0026] Figure 7 is a table of thermal performance data of each embodiment of the polyimide film of the present application. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in conjunction with the accompanying drawings.

[0028] In the present application, NBDA is the English abbreviation of the diamine monomer bicyclo[2.2.1]heptane dimethylamine; DMAC is the English abbreviation of N,N-dimethylacetamide; M-Tol is the English abbreviation of 2,2'-dimethyl-4,4'-diaminobiphenyl; BPADA is the English abbreviation of bisphenol A type diether dianhydride; ODPA is the English abbreviation of 4,4´-oxydiphthalic anhydride; PAA is the English abbreviation of polyamic acid.

[0029] A preparation method of a polyimide film, sequentially comprising the following steps:

[0030] Step A: Dissolve diamine monomer bicyclo[2.2.1]heptane dimethylamine (NBDA) and / or 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) in aprotic polar organic solvent N,N-dimethylacetamide (DMAC), introduce nitrogen (N2), stir until completely dissolved, to obtain a colorless or light transparent mixed solution; the mass percentage of N,N-dimethylacetamide (DMAC) in the mixed solution is 15% to 25%;

[0031] Step B: Quickly add bisphenol A type diether dianhydride (BPADA) or 4,4´-oxydiphthalic anhydride (ODPA) to the above mixed solution, maintain the introduction of nitrogen (N2), and after a period of reaction, obtain a colorless or light transparent polyamic acid (PAA) glue solution; the period of reaction in this step B is 6 hours to 24 hours, the reaction temperature is 0 ℃ to 50 ℃, and the total solid content is 15% to 25%;

[0032] The molar ratio of the bisphenol A type diether dianhydride (BPADA) or 4,4´-oxydiphthalic anhydride (ODPA) to the bicyclo[2.2.1]heptane dimethylamine (NBDA) or 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1 to 1.02):1;

[0033] Or, the molar ratio of the bisphenol A dioxane dianhydride (BPADA) or 4,4'-oxydiphthalic anhydride (ODPA) to the total amount of the bicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1-1.02):1; the molar ratio of the bicyclo[2.2.1]heptane dimethylamine (NBDA) to 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (10-0):(0-10).

[0034] Step C: drop the polyamide acid glue solution on a clean tool plate, for example, on a clean glass plate, and use a four-sided preparation device to coat the tool plate, for example, the glass plate, uniformly at the required thickness, place it in an oven for thermal imidization, which can be performed at 80 ℃ / h (vacuum), 120 ℃ / h (vacuum), 150 ℃ / h (vacuum), 200 ℃ / h, 250 ℃ / h, then take out the tool plate, for example, the glass plate, and naturally cool it to room temperature, then place the tool plate, for example, the glass plate, in warm water, which is water at 40-60 ℃, until the film coated on the tool plate, for example, the glass plate, falls off the glass plate, then place the film in a blast oven for drying, the temperature of the blast oven drying is 80-120 ℃, the drying time is 0.5-1.5 hours, for example, the temperature of the blast oven drying is 100 ℃, the drying time is 1.0 hour, after cooling, a polyimide film is obtained. 80 ℃ / h (vacuum), 120 ℃ / h (vacuum) are performed in a vacuum state in an early stage using a vacuum pump, 200 ℃ / h, 250 ℃ / h are generally performed in another high-temperature oven.

[0035] The application also provides a polyimide film obtained by the above-mentioned preparation method of a polyimide film, the polyimide film of the application comprising N,N-dimethylacetamide (DMAC), bisphenol A dioxane dianhydride (BPADA) or 4,4'-oxydiphthalic anhydride (ODPA), and bicyclo[2.2.1]heptane dimethylamine (NBDA) and / or 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) as diamine monomers.

[0036] That is, the polyimide film of the application comprises N,N-dimethylacetamide (DMAC), bisphenol A dioxane dianhydride (BPADA) and bicyclo[2.2.1]heptane dimethylamine (NBDA) as diamine monomers; wherein the molar ratio of the bisphenol A dioxane dianhydride (BPADA) to the bicyclo[2.2.1]heptane dimethylamine (NBDA) is (1-1.02):1, and the N,N-dimethylacetamide (DMAC) accounts for 15-25% of the mixed solution.

[0037] Or the polyimide film of the present application comprises N,N-dimethylacetamide (DMAC), bisphenol A type diether dianhydride (BPADA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol); wherein the molar ratio of bisphenol A type diether dianhydride (BPADA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1-1.02):1, and N,N-dimethylacetamide (DMAC) accounts for 15%-25% of the mixed solution.

[0038] Or the polyimide film of the present application comprises N,N-dimethylacetamide (DMAC), bisphenol A type diether dianhydride (BPADA), dicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol); wherein the molar ratio of bisphenol A type diether dianhydride (BPADA) and the total amount of dicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1-1.02):1; the molar ratio of dicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (10-0):(0-10), and N,N-dimethylacetamide (DMAC) accounts for 15%-25% of the mixed solution.

[0039] Or the polyimide film of the present application comprises N,N-dimethylacetamide (DMAC), 4,4´-oxydiphthalic anhydride (ODPA) and dicyclo[2.2.1]heptane dimethylamine (NBDA); wherein the molar ratio of 4,4´-oxydiphthalic anhydride (ODPA) and dicyclo[2.2.1]heptane dimethylamine (NBDA) is (1-1.02):1, and N,N-dimethylacetamide (DMAC) accounts for 15%-25% of the mixed solution.

[0040] Or the polyimide film of the present application comprises N,N-dimethylacetamide (DMAC), 4,4´-oxydiphthalic anhydride (ODPA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol); wherein the molar ratio of 4,4´-oxydiphthalic anhydride (ODPA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1-1.02):1, and N,N-dimethylacetamide (DMAC) accounts for 15%-25% of the mixed solution.

[0041] Or the polyimide film of the application comprises N,N-dimethylacetamide (DMAC), 4,4'-oxydiphthalic anhydride (ODPA), dicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) of a diamine monomer; wherein the molar ratio of 4,4'-oxydiphthalic anhydride (ODPA) to the total amount of dicyclo[2.2.1]heptane dimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (1-1.02):1; the molar ratio of dicyclo[2.2.1]heptane dimethylamine (NBDA) to 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is (10-0):(0-10), and N,N-dimethylacetamide (DMAC) accounts for 15%-25% of the mixed solution.

[0042] The polyimide film of the application is applied in the fields of packaging, microelectronic manufacturing and solar substrates, for example, as a base film of a flexible printed circuit (FPC), a chip-scale package (CSP) and the like, and is particularly applied in an object of a display requiring high optical transparency. Embodiment

[0043] A preparation method of a polyimide film, sequentially comprising the following steps:

[0044] Step A: 5.3980 grams of DMAC solvent, 0.3085 grams of NBDA (2mmol) are added to a 250 milliliter three-necked flask under room temperature (25-30 ℃) conditions, nitrogen (N2) is introduced, and magnetic stirring is started to obtain a colorless transparent mixed solution; mmol is millimole;

[0045] Step B: 1.0410 grams of bisphenol A type diether dianhydride BPADA (2mmol) is quickly added to the above mixed solution, the total solid content is 20%, a large amount of white flocculent precipitate appears after the addition of BPADA, the precipitate is completely dissolved after magnetic stirring for about 3-5 minutes, nitrogen (N2) is continuously introduced, and a colorless transparent polyamic acid (PAA) glue solution is obtained after 24 hours of reaction;

[0046] Step C: The polyamic acid glue solution above is dropped on a clean glass plate and coated uniformly on the glass plate with a four-side coater. The glass plate is placed in an oven and heated at 80 ℃ / h (vacuum), 120 ℃ / h (vacuum), 150 ℃ / h (vacuum), 200 ℃ / h, and 250 ℃ / h to remove the solvent (i.e., heat imidization) and then taken out and naturally cooled to room temperature. Then the glass plate is placed in warm water until the film formed by the polyamic acid glue solution coated on the glass plate falls off the glass plate. The film is then placed in a blast oven and dried at 100 ℃ for 1 hour. After cooling, a nearly colorless and transparent polyimide film with a thickness of 40 microns is obtained, which is marked as PI-1. In this example, the molar ratio of bisphenol A diether dianhydride (BPADA) and bicyclo[2.2.1]heptane dimethylamine (NBDA) is 1:1, and N,N-dimethylacetamide (DMAC) accounts for 20% of the total mixed solution. Example

[0047] The same as Example 1, except that the substances and amounts added in Step B are different. In this example, ODPA is used instead of BPADA in Step B of Example 1. The amount of ODPA in Step B of this example is 0.6204 grams, 2 mmol, and the total solid content is also 20%. A nearly colorless and transparent polyimide film is also obtained in Step C of this example, and the thickness of the polyimide film is also 40 microns, which is marked as PI-2. In this example, the molar ratio of 4,4´-oxydiphthalic anhydride (ODPA) and bicyclo[2.2.1]heptane dimethylamine (NBDA) is 1:1, and N,N-dimethylacetamide (DMAC) accounts for 20% of the total mixed solution. Example

[0048] The same as Example 1, except that the substances and amounts added in Step A are different. Specifically:

[0049] Step A: At room temperature (25-30 ℃), 5.6304 grams of DMAC solvent, 0.1543 grams of NBDA (1 mmol), and 0.2123 grams of M-Tol (1 mmol) are added to a 250-milliliter three-necked flask, nitrogen gas (N2) is introduced, and magnetic stirring is started until complete dissolution, obtaining a light-colored transparent mixed solution;

[0050] The polyamic acid (PAA) glue solution obtained in Step B is light-colored and transparent;

[0051] The polyimide film obtained in Step C is light-colored and transparent, and the thickness of the polyimide film is also 40 microns, which is marked as PI-3.

[0052] In this third example, the molar ratio of bisphenol A type diether dianhydride (BPADA), bicyclo[2.2.1]heptanedimethylamine (NBDA) and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is 10:5:5. Example

[0053] This is basically the same as Example 3, except that the substances and amounts in step B are slightly different, specifically:

[0054] Step B: Quickly add 0.6204 g of ODPA (2 mmol) to the mixed solution in Step A. The total solid content is 20%. After adding ODPA, a large amount of white flocculent precipitate will appear. After magnetic stirring for about 3 to 5 minutes, the precipitate will be completely dissolved. Nitrogen gas (N2) is kept in the air. After reacting for 24 hours, a light-colored transparent polyamic acid (PAA) solution is obtained.

[0055] The polyimide film obtained in step C is also light-colored and transparent, and its thickness is 40 micrometers, labeled as PI-4.

[0056] In this fourth example, the molar ratio of 4,4'-oxophthalic anhydride (ODPA), bicyclo[2.2.1]heptanedimethylamine (NBDA), and 2,2'-dimethyl-4,4'-diaminobiphenyl (M-Tol) is 10:5:5.

[0057] The properties of the polyimide films prepared in Examples 1 to 4 above were measured:

[0058] I. Determination of Fourier Transform Infrared Spectroscopy

[0059] Measurements were taken using a TENSOR27 Fourier transform infrared spectrometer from Bruker GmbH, Germany, in total reflectance (ATR) mode, with a measurement range of 4000–600 cm⁻¹. -1 (centimeter -1 The scan was performed 32 times, with a resolution of 4 cm. -1 .

[0060] Figure 1 The images show the infrared spectra of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4. Figure 1 The peaks marked are characteristic absorption peaks of polyimide films. Among them, 1772 cm⁻¹ is the peak value. -1 1709 cm -1 740 cm -1 The absorption peaks at 1361 cm⁻¹ correspond to the asymmetric stretching vibration peak, the symmetric stretching vibration peak, and the bending vibration peak of the C=O ring on the polyimide ring, respectively; -1The absorption peak at 2871–2949 cm⁻¹ corresponds to the CN stretching vibration peak on the imide ring. -1 The absorption peak at 3400 cm⁻¹ is a characteristic absorption peak of the saturated CH bond on the diamine monomers NBDA and M-Tol; -1 No characteristic absorption peaks of amino groups were observed nearby, nor were characteristic absorption peaks of polyamic acid (PAA) at 1660 cm⁻¹. -1 and 1550 cm -1 The characteristic absorption peak at this location indicates that the polyimide has been completely imidized.

[0061] II. Ultraviolet Optical Performance Testing

[0062] The ultraviolet optical properties of polyimide films were measured using a UV-2550 ultraviolet spectrometer manufactured by Shimadzu Corporation of Japan, with air as a control, and the wavelength range was 200–800 nm.

[0063] Figure 2 The UV-Vis spectra of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4 are shown below. Figure 3 This is a summary table of UV data for the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4.

[0064] from Figure 3 The UV data summary table shows that the cutoff wavelength of the polyimide film is in the range of 355–367 nm; the transmittance at 450 nm is between 79.11% and 84.31%, all of which are higher than 81% except for PI-3; the maximum transmittance at 800 nm is between 87.54% and 89.13%, all of which are higher than 87%. In summary, the four PI films have good UV transmittance. Even after introducing the aromatic diamine M-Tol, the PI film still has good UV transmittance. This is because the introduced NBDA is a non-coplanar alicyclic diamine containing a mixture of isomers, and the molecular chain contains methylene and ether bonds. This can effectively reduce the conjugation degree of the PI molecular chain, inhibit the formation of charge transfer complexes (CTC) within the molecular chain, and the disordered arrangement of different isomers can destroy the symmetry and regularity of the PI chain, weaken the intermolecular forces, and thus improve the color of the film.

[0065] III. Determination of Thermal Properties

[0066] The glass transition temperature (Tg) of the polyimide film was measured using a differential scanning calorimeter (TA Instruments, Inc., Model Q20) under nitrogen (N2) atmosphere at a flow rate of 50 mL / min. -1The temperature was increased from 40 °C to 250 °C or 300 °C at a heating rate of 20 °C / min, and the cycle was repeated twice. The result of the second test was taken as the glass transition temperature of the PI film.

[0067] The thermal stability of polyimide films was determined using a thermogravimetric analyzer (model 209F3) from Netzsch GmbH (German Mechanical Engineering Group). Under nitrogen (N2) conditions, with an N2 flow rate of 20 mL•min⁻¹ and a heating rate of 20 ℃•min⁻¹, the TGA data of the PI films were obtained by heating from 40 ℃ to 800 ℃.

[0068] Figure 4 The figures show the DSC curves of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4. DSC stands for Differential Scanning Calorimetry. Figure 4 In the DSC curve, the horizontal axis represents temperature in °C, and the vertical axis represents heat flow rate, which is the amount of heat absorbed or released per unit mass of sample per unit time in watts per gram (W / g).

[0069] Figure 5 The graphs show the thermogravimetric analysis (TGA) curves of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4. The horizontal axis represents temperature in °C, and the vertical axis represents mass fraction as a percentage.

[0070] Figure 6 The graphs show the micro-quotient thermogravimetric analysis (DTG) curves of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4. The vertical axis represents DTG, in % / min, and the horizontal axis represents temperature, in °C.

[0071] Figure 7 This is a summary table of thermal performance data for various embodiments of polyimide films.

[0072] Depend on Figure 4 and Figure 7 As can be seen from the table, the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4 have high glass transition temperatures (T0). g ), glass transition temperature (T) g The glass transition temperature (T) of PI-3 ranges from 152.77 to 205.64 °C, all above 152 °C. g The glass transition temperature (T) of PI-1 is higher than that of PI-1. gThe glass transition temperature (Tg) of PI-4 is 30.08℃ higher than that of PI-2. g The glass transition temperature (T0) is 45.82 °C higher because M-Tol has a biphenyl structure. Introducing it into the PI chain enhances the chain rigidity, thereby restricting chain movement. Therefore, the glass transition temperature (T0) is higher. g The results show that the introduced aromatic diamine monomer M-Tol can significantly improve the heat resistance of PI film without significantly reducing its optical properties.

[0073] Depend on Figure 5 , Figure 6 and Figure 7 As can be seen from the table, the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4 have higher initial thermal decomposition temperatures (T). d ) and the temperature corresponding to the maximum decomposition rate (T) dmax ); where the initial thermal decomposition temperature (T) d The temperature range is approximately 480 ℃, specifically 479.0–485.2 ℃; the maximum decomposition rate (T) is around 480 ℃. dmax The corresponding temperatures range from 499.2 to 503.8 °C, with little difference among the four. The char residue (Ri) of the polyimide films PI-1 to PI-4 obtained in Examples 1 to 4 at 800 °C... w800 All of them are above 20%, among which the R of polyimide film PI-3 is above 20%. w800 R of polyimide film PI-1 w800 The R of polyimide film PI-4 is 24.35% higher. w800 R of polyimide film PI-2 w800 The difference is 22.28% higher because the M-Tol introduced into polyimide films PI-3 and PI-4 has a biphenyl structure, which introduces a large number of benzene ring structures into the molecular chain, thus increasing its thermal stability. Combined with the UV optical performance test data of the PI film, it shows that the introduced aromatic diamine monomer M-Tol can significantly increase the thermal stability of the polyimide film without significantly reducing its optical performance.

[0074] Compared with the prior art, the high-thermal-stability light-colored or even colorless transparent polyimide film obtained by the application adopts a binary polymerization and ternary copolymerization mode, the binary polymerization obtains high-thermal-stability light-colored or even colorless transparent polyimide film, and on the basis of the binary polymerization, the ternary copolymerization mode is adopted to introduce aromatic diamine M-Tol, so as to obtain light-colored or even colorless transparent polyimide film with good optical transparency and thermal performance. The preparation method of the application is simple and environment-friendly. Through infrared spectrum, ultraviolet optical and thermal performance characterization analysis, it is determined that the high-thermal-stability light-colored or even colorless transparent polyimide film has been successfully synthesized.

[0075] The above-mentioned examples only express the preferred embodiments of the application, and the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope of the application; it should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application; therefore, all equivalent transformations and modifications within the scope of the claims of the application should belong to the coverage of the claims of the application.

Claims

1. A method for producing a polyimide film, characterized by comprising the steps of: Sequentially comprising the following steps: ​ Step A: Dissolve diamine monomer bicyclo[2.2.1]heptane dimethylamine or 2,2'-dimethyl-4,4'-diaminobiphenyl in solvent N,N-dimethylacetamide, introduce nitrogen, stir until completely dissolved, to obtain a mixed solution; Step B: Add bisphenol A type diether dianhydride or 4,4'-oxybisphthalic anhydride to the above mixed solution, maintain nitrogen introduction, after a period of reaction, obtain a polyamic acid glue solution; Step C: Drop the above polyamic acid glue solution on a tool plate, and coat uniformly on the tool plate according to the required thickness, put into an oven for thermal imidization, then take out the tool plate, naturally cool to room temperature, then put the tool plate into warm water until the film coated on the tool plate falls off from the tool plate, then place the film in an oven for drying, after cooling, obtain a polyimide film.

2. The polyimide film preparation method according to claim 1, characterized in that: In step A, the mass percentage of N,N-dimethylacetamide in the mixed solution is 15% to 25%.

3. The polyimide film preparation method according to claim 1, characterized in that: The molar ratio of the bisphenol A type diether dianhydride or 4,4'-oxybisphthalic anhydride to the bicyclo[2.2.1]heptane dimethylamine or 2,2'-dimethyl-4,4'-diaminobiphenyl is (1-1.02):

1.

4. A method for producing a polyimide film, characterized by comprising the steps of: Sequentially comprising the following steps: Step A: Dissolve diamine monomer bicyclo[2.2.1]heptane dimethylamine and 2,2'-dimethyl-4,4'-diaminobiphenyl in solvent N,N-dimethylacetamide, introduce nitrogen, stir until completely dissolved, to obtain a mixed solution; Step B: Add bisphenol A type diether dianhydride or 4,4'-oxybisphthalic anhydride to the above mixed solution, maintain nitrogen introduction, after a period of reaction, obtain a polyamic acid glue solution; Step C: Drop the above polyamic acid glue solution on a tool plate, and coat uniformly on the tool plate according to the required thickness, put into an oven for thermal imidization, then take out the tool plate, naturally cool to room temperature, then put the tool plate into warm water until the film coated on the tool plate falls off from the tool plate, then place the film in an oven for drying, after cooling, obtain a polyimide film.

5. The polyimide film preparation method according to claim 4, characterized in that: In step A, the mass percentage of N,N-dimethylacetamide in the mixed solution is 15% to 25%.

6. The polyimide film preparation method according to claim 4, characterized in that: The molar ratio of the bisphenol A type diether dianhydride or 4,4'-oxybisphthalic anhydride to the total amount of the bicyclo[2.2.1]heptane dimethylamine and 2,2'-dimethyl-4,4'-diaminobiphenyl is (1-1.02):1; the molar ratio of the bicyclo[2.2.1]heptane dimethylamine to 2,2'-dimethyl-4,4'-diaminobiphenyl is (10-0):(0-10).

7. A polyimide film, characterized in that: The polyimide film according to any one of claims 1 to 6.

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